The present invention relates generally to the field of medical catheters and similar devices used to make internal measurements. More particularly, the invention relates to catheters that include microminiature sensors for detecting and/or measuring various physiological parameters.
Catheters with integrated physiologic sensors have a variety of applications. For example, sensing catheters enable the measurement of various physiological parameters, such as blood pressure, blood flow, temperature, thermal gradients, and various chemistries. Due to their minimally invasive design, these catheters can measure these parameters at remote sites within a patient.
While a small circumference allows a catheter to enter and navigate through tight spaces, such as the vasculature and other body lumens, it also makes it difficult to add additional functionality to the catheter. For example, integration of physiological sensors into a catheter can prove difficult because the sensor must be integrated within the narrow spaces of the catheter. Also, any required electrical bus must be incorporated into the catheter. For example, U.S. Pat. No. 5,902,248 to Millar, et al. for a REDUCED SIZE CATHETER TIP MEASUREMENT DEVICE discloses a device that requires three leads for each sensor. Using this arrangement, the construction of a catheter with multiple sensors is difficult because numerous electrical leads must be packaged into the narrow geometries of the catheter. The use of an addressable electrical bus, such as that described in U.S. Pat. No. 5,113,868 to Wise, et al. for a ULTRAMINIATURE PRESSURE SENSOR WITH ADDRESSABLE READ-OUT CIRCUIT, reduces the need for multiple leads for each sensor.
Due to their relatively small size, microminiaturize sensors, also referred to as microsensors, microfabricated sensors, MEMS (micro electrical mechanical systems), and BioMEMS, provide excellent candidates for integration into catheter designs. However, even these small sensors have proven difficult to mechanically integrate into the relatively soft material of most catheters, such as plastics. Furthermore, even though microminiature sensors are relatively small, it is difficult to place these sensors in a specific location within a catheter during the manufacturing process. Also, it is often useful to include some type signal conditioning circuit with the sensor. Signal conditioning circuits modify or condition an output of the sensor such that it is in a form acceptable for use by an appropriate receiving and/or analyzing device. Ideally, the conditioning circuit is placed near the sensor to minimize noise effects on the raw sensor output signal. Thus, the conditioning circuit must also be placed within the catheter, which adds complexity to the manufacturing process.
Considering these and other drawbacks and difficulties, there is a need for a sensor module with an integrated signal conditioning circuit that facilitates catheter assembly. Also, there is a need for a sensing catheter system that includes an electrical bus that allows placement of multiple sensors in a catheter without necessitating multiple separate electrical leads for each sensor. Furthermore, there is a need for improved methods of fabricating sensing catheter systems.
The present invention provides a microminiature sensor module that includes a signal conditioning circuit and a physiological sensor. The module has electrical contacts that facilitate connection of the module to an electrical bus, such as within a sensing catheter.
The present invention also provides a sensing catheter system. In one embodiment, the system includes an electrical bus that provides electrical power and a signal return pathway to a microminiature sensor module. In one embodiment, the sensing catheter system comprises a catheter body having a circumferential wall and first and second lumens. The wall has at least one opening that exposes the second lumen. Two electrical leads are disposed in the second lumen, and can be used to provide electrical power and a return signal path. A microminiature sensor module is disposed in the opening and adjacent both of the electrical leads. Electrical contacts on the sensor module are in electrical communication with the two electrical leads. A sealant is disposed over the sensor module and fills the opening in the circumferential wall of the catheter body.
The present invention also provides methods of fabricating a sensing catheter system. A preferred method comprises forming a catheter body having a circumferential wall and first and second lumens, placing two electrical leads in the second lumen, forming an opening in the wall to expose the electrical leads, disposing a sensor module in the opening and adjacent the electrical leads, and placing the sensor module in electrical communication with the electrical leads. Lastly, the opening is sealed.
While the invention is defined by the claims appended hereto, additional understanding of the invention can be obtained by referencing the following description of preferred and alternate embodiments and the appended drawings.